Remove outdated banner for Katib docs

[andreyvelich]

All Katib docs should be up to date for 1.1 release from 11th of June, see this: kubeflow/katib#1211.

/cc @gaocegege @johnugeorge @jlewi

[kubeflow-bot]

This change is 

[gaocegege]

/lgtm

[andreyvelich]

/approve

[jlewi]

@andreyvelich @gaocegege Looks like you guys need an OWNERs file so you can approve your changes.

[andreyvelich]

@jlewi We have already created OWNERS file for hyperparameter-tuning section: https://github.com/kubeflow/website/blob/master/content/en/docs/components/hyperparameter-tuning/OWNERS.
This PR also makes changes for reference.
I created PR to add OWNERS file there: #2092

[andreyvelich]

@gaocegege @johnugeorge We need to get lgtm on this PR again.

[andreyvelich]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andreyvelich

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• content/en/docs/components/hyperparameter-tuning/OWNERS [andreyvelich]
• content/en/docs/reference/OWNERS [andreyvelich]

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[gaocegege]

/lgtm